# ---
# title: 1417. Reformat The String
# id: problem1417
# author: Tian Jun
# date: 2020-10-31
# difficulty: Easy
# categories: String
# link: <https://leetcode.com/problems/reformat-the-string/description/>
# hidden: true
# ---
# 
# Given alphanumeric string `s`. ( **Alphanumeric string** is a string
# consisting of lowercase English letters and digits).
# 
# You have to find a permutation of the string where no letter is followed by
# another letter and no digit is followed by another digit. That is, no two
# adjacent characters have the same type.
# 
# Return _the reformatted string_ or return **an empty string** if it is
# impossible to reformat the string.
# 
# 
# 
# **Example 1:**
# 
#     
#     
#     Input: s = "a0b1c2"
#     Output: "0a1b2c"
#     Explanation: No two adjacent characters have the same type in "0a1b2c". "a0b1c2", "0a1b2c", "0c2a1b" are also valid permutations.
#     
# 
# **Example 2:**
# 
#     
#     
#     Input: s = "leetcode"
#     Output: ""
#     Explanation: "leetcode" has only characters so we cannot separate them by digits.
#     
# 
# **Example 3:**
# 
#     
#     
#     Input: s = "1229857369"
#     Output: ""
#     Explanation: "1229857369" has only digits so we cannot separate them by characters.
#     
# 
# **Example 4:**
# 
#     
#     
#     Input: s = "covid2019"
#     Output: "c2o0v1i9d"
#     
# 
# **Example 5:**
# 
#     
#     
#     Input: s = "ab123"
#     Output: "1a2b3"
#     
# 
# 
# 
# **Constraints:**
# 
#   * `1 <= s.length <= 500`
#   * `s` consists of only lowercase English letters and/or digits.
# 
# 
## @lc code=start
using LeetCode

## add your code here:
## @lc code=end
